In the drug development field, there is a case where an influence of a drug administered to a sample such as a cell is evaluated by measuring light emitted from the cell. Patent Literature 1 discloses a method for evaluating a cell by performing image processing on a cell image of animals and plants. In this method, a protrusion protruded outward from a cell main body such as a nerve cell is extracted from a cell image by an image processing technique. In this image processing technique, a pixel having a luminance value that exceeds a predetermined threshold value is extracted as a subject to be analyzed from a plurality of pixels configuring an image.